Method of improving recovery of mineral values from ores



United States Patent Office 3,078,996 Patented Feb. 26, 1963 3,078,996 MEN-D OF fltdPROViNG RECOVERY OF MINERAL VALUES FROM ORES Robert E. Snow and Fred N. Oberg, Lalreland, Fla, as-

signors to international Minerals & Chemical Corporation, a corporation of New York No Drawing. Filed lune 28, 1957, Ser. No. 668,820

8 Claims. (Cl. 209166) This invention relates to the bencficiation of phosphate ores. More particularly, it relates to the treatment of the products of flotation with nitrogenous positive ion agents to render them susceptible to further processing. Still more particularly, it relates to a method of removing aliphatic amine reagents from flotation products.

Florida phosphate ore is generally beneficiated by flotation of the 35 +150 mesh standard screen size particles produced by the classification and screening, washing, and desliming treatments of phosphate matrix. In these well-known flotation operations, a slurry of the particles is admixed with negative ion agents such as tall oil, oleic acid and the like, and subjected to agitation and aeration in one or more flotation operations; the first operation generally being designated as a rougher separation and the concentrates therefrom being refloated in so-called cleaner and recleaner flotation operations.

Current practice in some phosphate, feldspar, and other beneficiation plants is to further upgrade the concentrates obtained by flotation with negative ion agents, through flotation with positive ion agents having an affinity for silica, such as the high molecular weight aliphatic amines containing an alkyl group or groups of twenty carbon atoms and their water soluble addition salts With acids. In the positive ion agent flotation, the silica and other gangue materials such as heavy minerals are overflowed in a froth and the phosphate is obtained as an underflow product.

While this method floats off the minor component (silica),

the separation is not highly selective and. ap-

preciable phosphate is floated off with the silica in a product which, while a relatively'small portion of the total ore being processed, i.e., 10 to nevertheless carries a high percentage, 10 to 30% BPL, to waste if the silica tail is not further processed. In order to be able to recycle this silica product to recover its phosphate con-' tent, it is necessary to remove the nitrogenous positive ion agent. Sulfuric acid, while effective to remove fatty acid reagent, is relatively ineffective to remove the nitrogenous positive ion agents. Slimes and clays of -150 mesh particle size have been shown to be moderately elfective in removing the nitrogen-bearing reagents permitting further processing to recover the heavy minerals and additional phosphate, but require large desliming and washing facilities.

It is a primary object of this invention to provide a method wherein nitrogenous positive ion reagents are removed from flotation products in a highly effective manner.

It is another object to provide a method of removing nitrogeneous positive ion reagent without addition of special equipment for handling the operation.

Now it has been discovered that nitrogenous positive ion reagents are removed from reagentized solid particles or degradated to the point of ineffectiveness by agitation of an aqueous slurry of reagentized particles in the pres ence of a halogen or halogens.

More in detail, the flotation product, bearing nitroge nous positive ion reagent thereon, is contacted by mixing into the slurry, water having chlorine in solution or by bubbling gaseous chlorine directly into the flotation operation products.

Generally, the froth product of the amine flotation product comprising silica, phosphate material, and heavy minerals, passes by launder to an accumulator, usually a sump. If water containing chlorine in solution is mixed with this accumulated slurry, the diluted slurry is thickened in a hydroseparator or equivalent apparatus, the reagent being removed in the discard or wash water.

It is not necessary, however, to eliminate the products of the reaction of amine reagent and halogen from contact with the solids before the solids can be further processed. If gaseous chlorine is bubbled through the slurry in the accumulator, the solids after water washing may be recycled to a fatty acid flotation stepwhere the feed corresponds in B PL content to the recycle material, as for example, to the rougher flotation operation.

The amount of halogen required varies. somewhat depending upon the amount of nitrogenous positive ion agent being used. v

In general, utilizing chlorine or bromine, amounts of halogen which effectively destroy the' hydrophobic amine coating range from about 0.15 pound to about 0.45 pound per ton of solids in the slurry mass although amounts outside this range may housed under special operating conditions. It will be recognized that various halogens have different solu-bilities in water, i.e., chlorine water is saturated at 28 C. with about 0.57% chlorine while bromine can be raised to about 3%, and that plant solutions should be kept at lower halogen concentrations.

When agitating the slurry mixture containing introduced halogen, the solids content of the slurry may vary from about 30% to 60% solids with 45 to 55% being considered as a good operative range. Agitation of the pulp is generally carried out for 3 to 5 minutes although the time is not too critical if subsequent processing, such as a reflotation, is to be employed. During the agitating a gaseous halogen may also be bubbled through the aqueous slurry mixture containing previously introduced halogen.

The invention will be further understood from a study of the following examples which are given by way of illustration and without any intention that the invention be limited thereto.

1 Example 1 Florida phosphate matrix was subjected to classification, desliming, washing, and screening operations in accordance with standard phosphate operating procedures to produce a 35 mesh flotation feed.

The flotation feed was subjected to amine flotation in a Denver cell at approximately 25% solids content using 1.4 pounds of Alamac 26 and 2 pounds of kerosene per ton of ore. The silica float product, or so-called amine tail, was divided into three fractions, A, B, and C.

To these fractions were added 0.08 pound, 0.14 pound, and 0.17 pound of chlorine per ton of tail solids and each fraction was agitated at 50% solids by vigorous stirring for three minutes.

After agitation, each slurry was dewatered by decanta tion and the solids fed to a Denver flotation cell without adding reagents so as to determine the amount of solids refloata-ble upon agitation and aeration.

Results were as follows:

The flotation feed cited in Example I was subjected as flotation using tall oil, kerosene, fuel oil and caustic soda and the phosphate concentrate obtained thereby was scrubbed with sulfuric acid to remove the reagents.

The washed concentrate was reagentized With a mixture of about 73% m-onooctadecyl amine and about 24% monohexadecyl amine in the form of the acetic acid addition salt. This reagentized concentrate in slurry form was subjected to a flotation operation in a Fagergren machine at approximately 30% solids content to recover a phosphate concentrate of approximately 77% BPL and a silica float product.

The amine flotation tail was divided into four fractions, A, B, C, and D. To these fractions were added 0.14 pound, 0.27 pound, 0.48 pound, and 1.20 pounds of chlorine per ton of tail solids and each fraction was agitated at 50% solids by vigorous stirring for three minutes.

After agitation, each slurry was dewatered by decantation and the solids fed to a Denver flotation cell without adding reagents so as to determine the amount of solids refloatable upon agitation and aeration.

Results were as follows: i

Example 111 A silica froth product overflowing from the amine flotation cells of the phosphate flotation circuit described in Example II assayed as follows: 22.1% BPL, 69.5% insoluble.

This silica froth product, which was a slurry of about 50% solids content, was dewatered to a solids content of about 70% and to the resultant slurry was added water and an amount of chlorine corresponding to approximately 1.2 pounds of chlorine per ton of solids. The slurry mixture was agitated for three minutes at 50% solids with a Lightning mixer, and then the solids were dewatered by 'decantation.

The dereagentized solids were converted to an aque ous pulp of about 60% solids content and reagentized with about 3.6 pounds of a reagent mixture comprising 25% tall oil, 25 kerosene, and 50% fuel oil per ton .of solids treated. Suflicient caustic soda was added to give the mixture a pH of between about 8.2 and 8.6.

The reagentized pulp was diluted to about 30% solids content and subjected to a single flotation operation in a Denver flotation machine.

Results were as follows:

Percent Percent Percent BIL Iusol. Heavy Minerals Feed 2-2. 06 69. 53 5. 46 T 11 8. 16 87. 58 0. 23 33. 39 54. 83 9. 73

slurry at least one halogen selected from the group consisting of chlorine and bromine, agitating the mixture and washing the solids.

2. The method of dereagentizing products obtained by flotation of finely divided ore with amine flotation agents which comprises preparing an aqueous slurry of said product of about 30 to 60% solids content, adding to said slurry at least one halogen selected from the group consisting of chlorine and bromine, agitating the mixture three to five minutes and washing the solids.

3. The method of dereagentizing products obtained by flotation of finely divided ore with amine flotation agents which comprises preparing an aqueous slurry of said product of about 30 to 60% solids content, adding to said slurry between about 0.15 pound and 0.45 pound of at least one halogen selected from the group consisting of chlorine and bromine per ton of solids being treated, agitating the mixture and washing the solids.

4. The method of dereagentizing products obtained by flotation of finely divided ore with amine flotation agents which comprises preparing an aqueous slurry of said product of about 30 to 60% solids content, adding to said slurry at least one halogen selected from the group consisting of chlorine and bromine, agitating an aqueous slurry of reagentized solids and bubbling at least one gaseous halogen selected from the group consisting of chlorine and bromine thercthrough, and washing the solids.

5. The method of dereagentizing products obtained by flotation of finely divided ore with amine flotation agents which comprises preparing an aqueous slurry of said product of about 30 to 60% solids content, introducing into said aqueous slurry gaseous chlorine, in quantities less than that required for saturation, agitating the mixture and washing the solids.

6. The method of dcreagentizing products obtained by flotation of finely divided ore with an amine flotation agent which comprises preparing an aqueous slurry of said product of from about 30 to about 60% solids content, agitating said aqueous slurry and bubbling at least one halogen selected from the group consisting of chlorine and bromine therethrough, and washing the solids.

7. The method which comprises dereagentizing reagentized solids obtained by flotation of materials with a nitrogenous positive ion flotation reagent selected from the group consisting of amines, amine-acid salts and mixtures thereof by agitating an aqueous slurry of said reagentized solids in the presence of at least one halogen selected from the group consisting of chlorine and bromine.

8. A method which comprises dereagentizing a reagentized silica float product obtained in a flotation beneflciation of phosphatic ore with a nitrogenous positive ion flotation reagent selected from the group consisting of amines, amine-acid salts and mixtures thereof by agitating an aqueous slurry of said reagentized silica float product in the presence of at least one halogen selected from the group consisting of chlorine and bromine.

References Cited in the file of this patent UNITED STATES PATENTS pages 1216-1218. 

1. THE METHOD OF DEREAGENTIZING PRODUCTS OBTAINED BY FLOTATION OF FINELY DIVIDED ORE WITH AMINE FLOTATION AGENTS WHICH COMPRISES PREPARING AN AQUEOUS SLURRY OF SAID PRODUCT OF ABOUT 30 TO 60% SOLIDS CONTENT, ADDING TO SAID SLURRY AT LEAST ONE HALOGEN SELECTED FROM THE GROUP CONSISTING OF CHLORINE AND BROMINE, AGITATING THE MIXTURE AND WASHING THE SOLDDS. 